1. Field of the Invention
The present invention relates to a workpiece transfer apparatus, a workpiece mounting apparatus and a workpiece mounting method. In the transfer apparatus the workpiece, for example an electronic device such as a bare chip IC is transferred, and in the mounting apparatus the workpiece is mounted on a substrate.
2. Description of the Related Art
PCT international Application Laid-Open No. WO2003/041478 discloses a mounter in which a pattern for positioning of a workpiece and a pattern for positioning of a substrate are in the same direction and imaged at the same time through a transmissive outside part of an suction hole of a transparent nozzle when the mounter mounts the workpiece on the substrate using the transparent nozzle to pick up by negative pressure. Japanese Patent Application Laid-Open No. 2004-069612 is discloses a configuration in which an opening of a directional lighting device having both directional and diffusional characteristics is positioned on the same axis of an optical axis of a camera. Japanese Patent Application Laid-Open No. 10-308431 discloses a configuration which enables both to pick up a workpiece and to recognize the workpiece visually from upside by means of using a transparent nozzle.
Generally, a plurality of electronic devices especially bare chip ICs etc. is made of a wafer 200 formed and arranged a matrix of laminated patterns thereon as shown in FIG. 5, and each semiconductor component with the patterns is made by cutting the wafer 200 along cutting lines 201. Usually a predetermined width from the cutting line 201 is remained as a cutting margin on which any pattern or the like is not formed for stabilization of yield in the cutting process as shown in FIG. 6.
Generally, a positioning mark for detecting a position of the electronic device is formed with a high degree of accuracy because the positioning mark is formed in the same process (photolithography etc.) of the pattern of the electronic device. Further, instead of the positioning mark, the pattern on a surface of the electronic device is often used as a fiducial mark, too.
Many electronic devices (hereinafter “workpieces”) became to be reduced size, and recently the size of some workpiece became to be less than 0.2 mm square. By necessity, a hole diameter of a workpiece pickup nozzle of a mounting apparatus is necessary to be less than one side of the workpiece.
Further, the hole diameter of the suction hole of the transparent nozzle is necessary to be more reduced diameter so as not to interfere with the pattern for positioning (as the fiducial mark) of the workpiece, if the method which disclosed in WO2003/041478 (detecting the pattern for positioning optically through the transparent nozzle) is applied. For instance, further more reducing of the diameter is demanded so that the pattern for positioning of the workpiece is not positioned inside of the suction hole of the transparent nozzle.
However it seems to be unrealistic to make the size of the suction hole smaller enabling to detect the pattern for positioning optically through the outside part of the suction hole of the transparent nozzle because forming the hole to the transparent body almost reaches to a process limitation. Specific explanation of an example of workpiece 100 is shown in FIG. 7. The workpiece 100 has bonding electrodes (bumps) 102 on a bonding face (under surface) facing to a substrate 110, and a pattern for positioning 101 for alignment (in FIG. 7, a predetermined pattern is used) is provided on an upper surface of the workpiece. Alternatively, a plurality of patterns for positioning 101 may be provided on the upper surface. Further, a pattern for positioning 111 for alignment is provided on the substrate 110, or preferably a plurality of marks 111 may be provided on the substrate 110. Hereinafter the pattern for positioning of the workpiece 100 shall be referred to as “the first pattern for positioning” that is used as a first fiducial mark, and the pattern for positioning of the substrate 110 shall be referred to as “the second pattern for positioning” that is used as a second fiducial mark. As shown in FIG. 8A, in case of a comparatively large workpiece (conventional workpiece), it is possible to detect the first pattern for positioning of the workpiece optically through the outside part of the suction hole of the transparent nozzle 215. But, as shown in FIG. 8B, in case of a smaller workpiece (recent workpiece), it is not possible to detect the first pattern for positioning of the workpiece optically through the outside part of the suction hole of the transparent nozzle. Because all or almost all of the patterns are positioned inside of the hole diameter of the suction hole even if the hole diameter of the transparent nozzle was reduced to the process limitation.
On the other hand, when a suction pathway 211 to the suction hole 210 of a transparent nozzle 215 is bent as L-shape as shown in FIG. 9A, it is not possible to detect the pattern for positioning of the workpiece 100 through the suction hole 210, because inner surface (usually cylindrical) of the bent part 212 of the suction pathway 211 interferes with a field of view of an imaging unit 250. In case of the suction pathway 211 is not bent as shown in FIG. 9B, it is also not possible to detect the pattern for positioning of the workpiece 100 through the suction hole 210, because a joint 220 for suctioning interferes with the field of view of the imaging unit 250. As mentioned above, it becomes to be difficult to detect the pattern for positioning on the upper surface of the workpiece along with downsizing of the workpiece.